JP5641951B2 - Wireless communication system, wireless communication method, wireless device, and data transmitter - Google Patents

Description

  The present invention relates to a wireless communication system and a wireless communication method, and more particularly, to a wireless communication system and a wireless communication method capable of introducing a system using RFID (Radio Frequency IDentification) technology in a wireless network environment.

  In recent years, a system using RFID attracts attention and has begun to be applied to various uses. The basic configuration of a system using an RFID includes an RFID reader / writer that performs data communication with an RFID wireless tag via radio, and a computer terminal that controls the RFID reader / writer. An RFID reader / writer can read or write data stored in a wireless tag (see Non-Patent Document 1).

  The RFID wireless tag does not include a battery because it generates a power supply voltage using wireless radio waves when transmitting / receiving data to / from the RFID reader / writer. Such a wireless tag is generally called a “passive type”. Specifically, an RFID wireless tag rectifies radio waves (part of a carrier wave) supplied from an RFID reader / writer from alternating current to direct current using a full-wave rectifier. Then, after stepping up and down to a voltage suitable as a circuit power source using an internal voltage control circuit and a booster circuit, this power is supplied as a power source for internal circuits such as a current mode demodulator and logic. In this case, the conversion efficiency from alternating current to direct current in the RFID wireless tag is determined by optimizing the element size of the PMOS / NMOS rectifier diode included in the full-wave rectifier, the parasitic capacitance before being input to the rectifier diode, etc. This can be increased by suppressing loss due to mismatch and loss due to mismatch between the antenna and the rectification input section.

  Patent Document 1 discloses a technique related to a room intruder detection device. The indoor intruder detection device disclosed in Patent Literature 1 includes a transmission device, a reception device, and an alarm device. The transmitter transmits an unmodulated wave signal having a predetermined carrier frequency. The reception device receives a signal output from the transmission device, a detection unit that detects the received signal, and outputs a detection signal when the level of the signal obtained by the detection exceeds a predetermined range. A level fluctuation detector. The alarm device issues an alarm based on the detection signal output from the level fluctuation detection unit of the receiving device. The indoor intruder detection device disclosed in Patent Literature 1 detects an intruder in the room from the variation in the received electric field of the radio wave output from the transmission device and the variation in the code error rate of the demodulated signal.

Japanese Patent Laid-Open No. 7-141577

International Solid Circuit Conference 2006 Proceedings No. 17.2

  As described in the background art, a dedicated RFID reader / writer is required to read data held by an RFID wireless tag (hereinafter also referred to as a data transmitter). Therefore, for example, in order to read data held by an RFID wireless tag in a wireless network (WLAN) environment, a dedicated RFID reader / writer connected to the wireless network by wire or wireless is required. For this reason, there is a problem that it is expensive to introduce a system using RFID technology in a wireless network environment.

  The wireless communication system according to the present invention modulates the first radio wave according to the first radio device that transmits the first data using the first radio wave and the second data to be transmitted. A data transmitter for outputting the second radio wave generated in step (b), and receiving the first radio wave and the second radio wave and transmitting from the first wireless device included in the received radio wave. And a second wireless device including a separation demodulation circuit that separates and demodulates the first data and the second data transmitted from the data transmitter.

  A wireless communication method according to the present invention uses a data transmitter in a wireless network including a first wireless device that transmits first data and a second wireless device that receives the first data. A wireless communication method for transmitting data, wherein the first data is transmitted from a first wireless device using a first radio wave, and the data transmitter transmits the first data according to the second data. A second radio wave is generated by modulating a radio wave, the second radio wave is output, the first radio wave and the second radio wave are received by the second wireless device, and the received radio wave The first data transmitted from the first wireless device and the second data transmitted from the data transmitter are separated and demodulated.

  In the wireless communication system and the wireless communication method according to the present invention, the data transmitter modulates the first radio wave according to the second data to be transmitted and outputs it as the second radio wave. Here, the modulated second radio wave acts as a disturbance to the first radio wave. Then, in the second wireless device, the first data transmitted from the first wireless device is separated from the second data transmitted from the data transmitter using the presence or absence of disturbance to the first radio wave, and the second data The first and second data are demodulated. This eliminates the need to provide a dedicated RFID reader / writer for reading data held by the data transmitter, thereby reducing the cost of introducing a system using RFID technology in a wireless network environment. it can.

  In addition, the data transmitter according to the present invention modulates the first radio wave used in the wireless network according to the sensor for acquiring the data to be transmitted and the data to be transmitted. A modulation circuit that generates a second radio wave that gives disturbance to the first radio wave.

  In addition, the wireless device according to the present invention is generated by modulating the first radio wave according to the first radio wave including the first data and the second data, and disturbs the first radio wave. And receiving the second radio wave to be applied, and separating and demodulating the first data and the second data contained in the received radio wave based on the bit error rate of the first radio wave A separation demodulation circuit.

  According to the present invention, it is possible to provide a wireless communication system and a wireless communication method capable of reducing the cost when introducing a system using RFID technology in a wireless network environment.

1 is a block diagram showing a wireless communication system according to a first exemplary embodiment; FIG. 6 is a diagram for explaining a bit error rate of radio waves received by the second wireless device according to the first embodiment; FIG. 3 is a block diagram showing another example of the wireless communication system according to the first exemplary embodiment. 6 is a block diagram illustrating another example of the second wireless device included in the wireless communication system according to the first embodiment; FIG. FIG. 3 is a block diagram showing a wireless communication system according to a second exemplary embodiment. FIG. 6 is a block diagram illustrating a second wireless device used in the wireless communication system according to the second embodiment. 6 is a flowchart for explaining an operation of the radio communication system according to the second exemplary embodiment; It is a figure for demonstrating the noise removal by a finite impulse response filter. It is a figure which shows the relationship between the carrier frequency of a radio | wireless communications system, and a data rate. 10 is a flowchart for explaining an operation of the wireless communication system according to the third exemplary embodiment; (A) It is a block diagram which shows the radio | wireless communications system concerning Embodiment 4. FIG. (B) It is a figure which shows an example of the disturbance which each of several data transmitters gives to a 1st electromagnetic wave. It is a figure which shows the S / N ratio at the time of using an M series PN code. FIG. 3 is a diagram for explaining a problem in the wireless communication system according to the first exemplary embodiment. FIG. 3 is a diagram for explaining a problem in the wireless communication system according to the first exemplary embodiment. FIG. 9 is a block diagram showing a wireless communication system according to a fifth exemplary embodiment. (A) is a block diagram which shows the detail of the data transmitter with which the radio | wireless communications system concerning Embodiment 5 is provided. (B) is a figure which shows an example of the specific circuit of the data transmitter shown to (a). FIG. 10 is a diagram for explaining a case where the condition of Expression 2 is satisfied in the wireless communication system according to the fifth embodiment. (A) is a block diagram which shows the data transmitter with which the radio | wireless communications system concerning Embodiment 6 is provided. (B) is a figure which shows an example of the specific circuit of the data transmitter shown to (a). (A) is a block diagram illustrating a data transmitter included in a wireless communication system according to a seventh embodiment. (B) is a figure which shows an example of the specific circuit of the data transmitter shown to (a). (A) is a block diagram showing a data transmitter with which the radio communications system concerning Embodiment 8 is provided. (B) is a figure which shows an example of the specific circuit of the data transmitter shown to (a). (A) is a figure for demonstrating the case where a data transmitter is attached to the adhesion member. (B) is sectional drawing for demonstrating the case where a data transmitter is attached to the adhesion member.

Embodiment 1
Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a block diagram of the wireless communication system according to the first embodiment. As shown in FIG. 1, the wireless communication system according to the present embodiment includes a first wireless device 1, a second wireless device 2, and a data transmitter (corresponding to a wireless tag for RFID) 3. Prepare. The first wireless device 1 transmits the first data using the first radio waves 12 and 13. The data transmitter 3 modulates the first radio wave 13 according to the second data to be transmitted and generates and outputs a second radio wave 14. The second wireless device 2 receives the first radio wave 12 and the second radio wave 14 and transmits the first data and data transmitted from the first radio device 1 included in the received radio wave. A separation / demodulation circuit 24 for separating and demodulating the second data transmitted from the machine 3 is provided. A feature of the wireless communication system according to the present embodiment is that disturbance from the data transmitter 3 such as RFID, which has been removed as noise in the prior art, is separated by the separation / demodulation circuit 24 of the second wireless device 2, and data It can be taken out as Hereinafter, each element which comprises the radio | wireless communications system concerning this Embodiment is demonstrated in detail.

  The first wireless device 1 includes an internal circuit (not shown) and an antenna 11 for realizing wireless communication with the second wireless device 2, and uses the first radio waves 12 and 13 for the first data. To send. Here, the first radio wave 12 is a direct wave transmitted directly to the second wireless device 2. The first radio wave 13 is transmitted to the data transmitter.

  The second wireless device 2 includes an internal circuit (not shown) and an antenna 23 for realizing wireless communication with the first wireless device 1. The separation / demodulation circuit 24 included in the second wireless device 2 includes the first data transmitted from the first wireless device 1 and the data transmitter 3 included in the received first and second radio waves. Separated from the transmitted second data. Further, the separation / demodulation circuit 24 demodulates the first data transmitted from the first wireless device 1 and the second data transmitted from the data transmitter 3, respectively.

  Here, the first wireless device 1 and the second wireless device 2 form a wireless network (WLAN). For example, the first wireless device 1 is a WLAN base station (WLAN master), and the second The wireless device 2 can be a WLAN receiver (WLAN slave). Further, for example, the first wireless device 1 and the second wireless device 2 are configured to be able to perform bidirectional communication. In the present embodiment, normal data communication between the first wireless device 1 and the second wireless device 2 uses internal circuits provided in the first wireless device 1 and the second wireless device 2, respectively. Implemented. Since normal data communication between the first wireless device 1 and the second wireless device 2 is the same as the conventional technology, detailed description thereof is omitted.

  In addition, the wireless communication system according to the present embodiment is not limited to WLAN, and can be widely applied to devices of existing wireless standards such as Bluetooth (registered trademark) and mobile phones in addition to WLAN. it can.

  The data transmitter 3 includes an antenna 31, a modulation circuit 32, and a sensor 33. The data transmitter 3 receives the first radio wave 13 output from the first wireless device 1 by the antenna 31 and uses the modulation circuit 32 to change the first radio wave 13 according to the second data to be transmitted. To generate and output a second radio wave 14. Here, the second data transmitted by the data transmitter 3 is data collected using the sensor 33, for example. The sensor 33 is, for example, a temperature sensor that measures a human body temperature, a pressure sensor that measures a human blood pressure, or the like. For example, the temperature of the measurement target can be sequentially checked by attaching a data transmitter with a built-in temperature sensor to the measurement target, wirelessly transmitting temperature information of the measurement target, and receiving the information on a wireless network.

  The sensor 33 is not limited to a temperature sensor and a pressure sensor, and any sensor can be used as long as it can acquire predetermined data. The second data transmitted by the data transmitter 3 may be data that the data transmitter 3 includes in advance. In this case, the data transmitter 3 may not include the sensor 33.

  For example, the modulation circuit 32 can generate the second radio wave 14 by load-modulating the first radio wave 13 according to the second data to be transmitted. The data transmitter 3 may include a power generation circuit 34 as in another example of the wireless communication system according to the present embodiment illustrated in FIG. That is, the power generation circuit 34 included in the data transmitter 30 illustrated in FIG. 3 receives the first radio wave (environmental radio wave) 13 using the antenna 31 and converts the first radio wave (environmental radio wave) 13 into a full-wave rectifier. To rectify from AC to DC. Then, after the voltage is stepped up and down to a voltage suitable as a circuit power source using an internal voltage control circuit and a booster circuit, this power can be supplied to the modulation circuit 32, the sensor 33, and the like. In this case, the data transmitter 30 does not need to be equipped with a battery, and constitutes a so-called passive data transmitter. On the other hand, the data transmitter 3 may include a battery, and in this case, a so-called active data transmitter is configured. In the case of the active type, the remaining amount of the battery may be included as the second data transmitted by the data transmitter 3.

Next, the operation of the wireless communication system according to the present embodiment will be described.
The first wireless device 1 and the second wireless device 2 constitute a wireless network (WLAN). At this time, the first wireless device 1 and the second wireless device 2 are configured to be able to communicate using the first radio wave 12 having a modulation element compliant with the standard.

  FIG. 2 is a diagram for explaining the bit error rate of radio waves (first radio wave 12 and second radio wave 14) received by the second wireless device 2. When there is no data transmission from the data transmitter 3, the first radio wave 12 is not affected by the second radio wave 14 transmitted from the data transmitter 3. That is, in this case, since the second radio wave 14 transmitted from the data transmitter 3 does not act as a disturbance to the first radio wave 12, the bit error rate does not increase as shown in FIG. Therefore, the first wireless device 1 and the second wireless device 2 can communicate with a low bit error rate 71 shown in FIG. Then, the second wireless device 2 receives the first radio wave 12 by the antenna 23, and the separation / demodulation circuit 24 demodulates the first data transmitted from the first wireless device 1.

  Next, the case where the data transmitter 3 transmits data will be described. In this case, first, the data transmitter 3 receives the first radio wave 13 output from the first wireless device 1. Further, the sensor 33 outputs the data acquired by the sensor 33 to the modulation circuit 32. Then, the modulation circuit 32 performs load modulation on the received first radio wave 13 in accordance with the data (second data to be transmitted) acquired by the sensor 33 and outputs the modulated radio wave as the second radio wave 14. (This operation is also called reflection.)

  When the data transmitter 3 transmits data, the first radio wave 12 is affected by the second radio wave 14 transmitted from the data transmitter 3 as shown in FIG. Therefore, in this case, since the second radio wave 14 transmitted from the data transmitter 3 works as a disturbance to the first radio wave 12, the bit error rate increases as indicated by reference numeral 72 in FIG.

  That is, the second radio wave modulated by load modulation in the data transmitter 3 disturbs the radio wave transmitted from the first wireless device 1 and lowers the reception SN ratio, and thus increases the bit error rate. That is, if load modulation of on / off keying is performed in the data transmitter 3, the second data can be transmitted using the time variation of the bit error rate as shown in FIG. Then, the second data transmitted from the data transmitter 3 can be demodulated by detecting the time variation of the bit error rate in the second receiving device 2.

  Note that the bit error rate 72 at this time is in a range lower than the wireless standard value of the bit error rate so as not to adversely affect the communication between the first wireless device 1 and the second wireless device 2. That is, both the bit error rate 71 and the bit error rate 72 are within a range lower than the wireless standard value of the bit error rate. In general, since the communication environment constantly changes and various disturbances (reflected waves) are mixed, a wireless standard is formulated so as to ensure communication robustness against such disturbances.

  The second wireless device 2 receives the first radio wave 12 and the second radio wave 14 with the antenna 23. The separation / demodulation circuit 24 separates the first data transmitted from the first wireless device 1 included in these received radio waves and the second data transmitted from the data transmitter 3, and These data are demodulated to generate demodulated data 25 from the first wireless device 1 and demodulated data 26 from the data transmitter 3.

  Here, the first data transmitted by the first wireless device 1 includes the first radio wave 12 having a modulation element conforming to the standards of the first wireless device 1 and the second wireless device 2 (that is, in accordance with the standard). Radio waves having a compliant carrier frequency). On the other hand, the second data transmitted by the data transmitter 3 uses a change in the bit error rate (that is, the level of the bit error rate) in the radio waves (first and second radio waves) received by the second wireless device 2. Is transmitted.

At this time, the period of change in the bit error rate of the radio wave received by the second wireless device 2 (that is, the modulation period of the bit error rate) is greater than the modulation period of the first radio wave 12 having a carrier frequency compliant with the standard. slow. For this reason, it is possible to separate the first data transmitted from the first wireless device 1 and the second data transmitted from the data transmitter 3 by using the separation / demodulation circuit 24.
For example, the separation / demodulation circuit 24 includes a low-pass filter (LPF), and by using the low-pass filter (LPF), it is possible to separate the second data having a low bit error rate modulation period. Further, for example, the separation / demodulation circuit 24 may include a band pass filter (BPF), and in this case as well, the second data having a low bit error rate modulation period is separated by using the band pass filter (BPF). be able to. Here, the band pass filter (BPF) can be configured by combining a low pass filter (LPF) and a high pass filter (HPF). At this time, by using a high-pass filter (HPF), the fluctuation component of the environmental radio wave whose modulation period is slower than the fluctuation period of the second data can be removed from the second data.
The separation / demodulation circuit 24 may be a filter circuit for an analog signal or a filter circuit for a digital signal after A / D conversion.

  FIG. 3 is a block diagram showing another example of the radio communication system according to the present embodiment. As shown in FIG. 3, the first radio wave 12 and the second radio wave 14 received by the antenna 23 of the second wireless device 2 may be amplified by an amplifier 27. Further, as shown in FIG. 3, a baseband filter 28 may be used as the separation / demodulation circuit 24. Further, a filter may be added as appropriate in accordance with the surrounding radio wave conditions, and the filter process may be performed in a strong frequency band of the second radio wave 14. The signal amplitude can be increased by the amplifier 27 and the filter processing to such an extent that the separation / demodulation circuit 24 (baseband filter 28) in the subsequent stage can perform the separation / demodulation processing.

  Further, the separation / demodulation circuit 24 included in the second wireless device 2 shown in FIG. 1 can also be configured as follows. FIG. 4 is a diagram illustrating a configuration of the second wireless device 22 of the wireless communication system according to the present embodiment. The second wireless device 22 shown in FIG. 4 includes an antenna 23, a receiving circuit 81, and a protocol processing unit 82, and this configuration is the same as that of an existing wireless device. Then, software processing is applied to the protocol processing unit 82 so that the protocol processing unit 82 of the second wireless device 22 operates as the separation / demodulation circuit 24. In this way, by performing software processing on the protocol processing unit 82, the second wireless device 2 shown in FIG. 1 can be configured using an existing wireless device. In the present embodiment, a part of the protocol processing unit shown in FIG. 4 may be configured by hardware. In this case, the software processing is applied to the second part other than the part configured by the hardware of the protocol processing unit. Wireless device 2 can be configured.

  That is, the first data transmitted by the first wireless device 1 includes the first radio wave 12 having a modulation element compliant with the standards of the first wireless device 1 and the second wireless device 2 (that is, compliant with the standard). Transmitted using a radio wave having a carrier frequency. On the other hand, the second data transmitted by the data transmitter 3 uses a change in the bit error rate (that is, the level of the bit error rate) in the radio waves (first and second radio waves) received by the second wireless device 2. Is transmitted. Then, the first data transmitted by the first wireless device 1 (that is, data transmitted at a carrier frequency compliant with the standard) and the second data transmitted by the data transmitter 3 are transmitted to the protocol processing unit 82. (Ie, data transmitted using a bit error rate modulated at a predetermined modulation frequency) is subjected to software processing so as to be separated and demodulated, whereby demodulated data 25 and data from the first wireless device 1 are processed. Demodulated data 26 from the transmitter 3 can be obtained. Such processing in the protocol processing unit 82 is performed in the baseband domain.

  Conventionally, in order to read data held by an RFID wireless tag (data transmitter) in a wireless network environment, a dedicated RFID reader / writer connected to the wireless network in a wired or wireless manner has been required. . For this reason, there is a problem that it is expensive to introduce a system using RFID technology in a wireless network environment.

  However, in the wireless communication system according to the present embodiment, the data transmitter 3 is the second transmission target in the wireless network environment configured by the first wireless device 1 and the second wireless device 2. A second radio wave 14 is generated and output by modulating the first radio wave 13 according to the data. Here, the modulated second radio wave 14 acts as a disturbance to the first radio wave 12. Then, in the separation / demodulation circuit 24 of the second wireless device 2, the first data transmitted from the first wireless device 1 and the data transmitter 3 are transmitted using the presence / absence of disturbance to the first radio wave 12. The second data is separated and the first and second data are demodulated.

  In the wireless communication system according to the present embodiment having such a configuration, it is not necessary to provide a dedicated RFID reader / writer in order to read data held by the RFID wireless tag (data transmitter 3). Therefore, the invention according to this embodiment can provide a wireless communication system capable of reducing the cost when introducing a system using RFID technology in a wireless network environment.

  Further, in the wireless communication system according to the present embodiment, the separation / demodulation circuit 24 shown in FIG. 1 is used for the protocol processing unit 82 of the second wireless device 22 having the existing hardware configuration shown in FIG. By performing software processing so as to operate, the second wireless device can be configured. Therefore, since the second wireless device according to the present embodiment can be configured simply by introducing software into an existing hardware configuration, the cost of introducing a system using RFID technology in a wireless network environment Can be reduced.

  Further, in the passive type data transmitter 3 that generates a power supply voltage using a radio wave, when power is supplied to the data transmitter 3 from a dedicated RFID reader / writer, there is a radio wave that does not go to the data transmitter 3. It was. That is, when the antenna of the RFID reader / writer has no directivity, there is wasted power without going to the data transmitter 3. Further, even if the antenna of the RFID reader / writer is given directivity to improve power transmission efficiency, there is power that is wasted in space rather than transmitting power by radio waves.

  On the other hand, in the wireless communication system according to the present embodiment shown in FIG. 3, a data transmitter is used by using radio waves (environmental radio waves) used for communication between the first wireless device 1 and the second wireless device 2. Thirty power generation circuits 34 generate power. Therefore, it is not necessary to newly introduce an RFID reader / writer and output power supply radio waves, so that power consumption of the wireless communication system can be reduced.

The technique disclosed in Patent Document 1 only detects the presence or absence of a disturbance, distinguishes a temporally varying disturbance from data, and determines an undesired disturbance generation source as a desired disturbance. I couldn't. That is, in such a wireless communication system, various disturbances (reflected waves) are mixed due to changes in the communication environment, and the bit error rate also changes accordingly. The technique disclosed in Patent Document 1 merely detects the presence or absence of a change in disturbance based on the bit error rate, and does not extract the desired disturbance as meaningful data.
On the other hand, in the wireless communication system according to the present embodiment, the second data (data transmitted from the data transmitter) having a low bit error rate modulation period is separated using a separation / demodulation circuit. 2 data is demodulated.
Therefore, acquisition of communication data from a desired disturbance, noise removal essential for establishment of wireless data communication, and communication partner in one-to-multiple communication, which was impossible with the technique disclosed in Patent Document 1, Sorting (refer to Embodiment 4 for details) is possible.

  Further, the wireless communication method according to the present embodiment includes a data transmitter in a wireless network including a first wireless device 1 that transmits first data and a second wireless device 2 that receives the first data. 3 is a wireless communication method for transmitting second data using 3, and includes the following steps. (1) A step of transmitting first data from the first wireless device 1 using the first radio waves 12 and 13. (2) A step of modulating the first radio wave 13 according to the second data in the data transmitter 3 to generate the second radio wave 14 and outputting the second radio wave 14. (3) The second radio equipment 2 receives the first radio wave 12 and the second radio wave 14, and the first data transmitted from the first radio equipment 1 included in the received radio wave Separating and demodulating the second data transmitted from the data transmitter 3;

  By the present invention according to this embodiment described above, it is possible to provide a wireless communication system and a wireless communication method capable of reducing the cost when introducing a system using RFID technology in a wireless network environment. it can.

Embodiment 2
Next, a second embodiment of the present invention will be described. FIG. 5 is a block diagram of a wireless communication system according to the second embodiment. In the wireless communication system according to the present embodiment, the second wireless device 21 includes the demodulation circuit 41 and the error rate evaluation circuit 42 as the separation demodulation circuit 24. The wireless communication according to the first embodiment described with reference to FIG. Different from the communication system. Since other than this is the same as in the case of the first embodiment, the same components are denoted by the same reference numerals, and redundant description is omitted.

  As illustrated in FIG. 5, the second wireless device 21 of the wireless communication system according to the present embodiment includes an amplifier 27, a demodulation circuit 41, and an error rate evaluation circuit 42. The amplifier 27 can be omitted as long as the signal levels of the first radio wave 12 and the second radio wave 14 are high, that is, if the signal level can be processed by the separation / demodulation circuit 24 in the subsequent stage. .

  The demodulation circuit 41 demodulates the first data transmitted from the first wireless device 1 included in the received radio wave, and outputs the demodulated data as demodulated data 25 from the first wireless device 1. . The error rate evaluation circuit 42 demodulates the first data transmitted from the first wireless device 1 and then evaluates the bit error rate. Based on the time variation of the bit error rate, the data from the data transmitter 3 is evaluated. Is demodulated, and demodulated data 26 from the data transmitter 3 is generated. In the wireless communication system according to the present embodiment, the demodulation circuit is only the demodulation circuit 41 that demodulates the first data transmitted from the first wireless device 1, and the data transmitted from the data transmitter 3. Are demodulated in the subsequent baseband processing.

  For example, when a third-party interference wave further enters the wireless communication system having such a configuration, the first radio wave from the first radio device 1 is compared with the second radio wave 14 from the data transmitter 3. When the radio wave (direct wave) 12 is in a dominant positional relationship, the reception SN ratio of the second data from the data transmitter 3 decreases. In such a case, the reception S / N ratio of the second data from the data transmitter 3 can be increased by performing the majority process and the code spreading process, and the data transmitter 3 in the second wireless device 21 can be increased. The second data from can be received.

  For example, the distance between the first wireless device 1 and the second wireless device 21 and the distance between the first wireless device 1 and the data transmitter 3 are equal, and the distance between the second wireless device 21 and the data transmitter 3 is equal. They are arranged as isosceles triangles that are half of them, and in the data transmitter 3, it is assumed that the reflection coefficient for reflecting the radio wave from the first wireless device 1 is about 0.5. In this case, compared to the distance directly entering the second wireless device 21 from the first wireless device 1, the distance indirectly entering the second wireless device 21 via the data transmitter is 1.5 times, Assuming that the reached power is proportional to the reciprocal of the square of distance, the indirect wave has a distance attenuation of 10 * log (1 / (1.5 * 1.5)) = − 4 dB compared to the direct wave. Further, since the reflection coefficient is 0.5, a reflection attenuation of 10 * log (0.5) = − 3 dB is added. As a result, the ratio between the power N at which radio waves from the first wireless device 1 directly enter the second wireless device 21 as noise and the power S that enters the second wireless device 21 as data via the data transmitter 3. Is a signal component attenuation amount = distance attenuation + reflection attenuation, and noise power is not increased or decreased, and S / N = −3 dB−4 dB = −7 dB, which is buried in noise.

However, for example, when the same data is transmitted 12 times from the data transmitter 3 and the majority process is performed in the second wireless device 2 to suppress random noise,
H (z ^-1 ) = 1 + z ^-1 + z ^-2 +… + z ^-11
As shown in FIG. 8, the 12-tap finite impulse response filter S / N defined by (1) is improved by 7.6 dB, so that data of S / N = −7 dB can be received.

  Here, as shown in FIG. 9, the data rate is at least 1 Mbps or more in the WLAN carrier frequency 2.4 GHz band. Therefore, since the environmental radio waves do not have periodicity at a low frequency where the data rate is lower than 1 Mbps, it is considered that the white light is sufficiently diffused in the communication band of the data transmitter 3. Therefore, the S / N ratio can be improved by executing the majority process. Since the majority process and code spreading process require redundancy, the effective data communication speed decreases. In this case, the scale of data that can be handled is smaller than that of a conventional RFID system.

  Next, the second wireless device 21 used in the wireless communication system according to the present embodiment will be specifically described with reference to FIG. 6 includes a demodulation unit 51, a demapping processing unit 52, a soft decision deinterleave Viterbi demodulation processing unit 53, and a frame processing unit 54.

  The demapping output from the demapping processing unit 52 is output to the soft decision deinterleave Viterbi demodulation processing unit 53 and the error rate evaluation circuit 42. The soft decision / Viterbi output from the soft decision deinterleave Viterbi demodulation processing unit 53 is output to the frame processing unit 54 and the error rate evaluation circuit 42. The frame processing output from the frame processing unit 54 is output as demodulated data 25 from the first wireless device 1. The frame processing output from the frame processing unit 54 is also output to the error rate evaluation circuit 42.

  The error rate evaluation circuit 42 includes a storage unit 61. The error rate evaluation circuit 42 demodulates the second data from the data transmitter 3 based on at least one of the demapping output, the soft decision / Viterbi output, and the frame processing output. Demodulated data 26 is output.

FIG. 7 is a flowchart for explaining the operation of the second wireless device 21 shown in FIG.
First, the first data transmitted from the first wireless device 1 is demodulated by the demodulator 51. The demodulated data demodulated by the demodulator 51 is branched from each layer of the protocol processing and output from the demodulating circuit 41 such as a bit string after demapping processing, a bit string after soft decision / Viterbi processing, and a bit string after frame processing. The As protocol processing proceeds in the demapping processing unit 52, soft decision deinterleave Viterbi demodulation processing unit 53, and frame processing unit 54, the influence of disturbances such as interference waves is alleviated. For this reason, the influence of disturbance is greater in the bit string after the demapping process than in the bit string after the frame process.

  Next, the bit error rate at the frame processing output is sampled (step S1). At this time, the bit error rate is sampled at a speed equal to or higher than the symbol rate of the data transmitted from the data transmitter 3. Then, the obtained sampling results are held in the storage unit in an array (step S2).

Next, the code despreading process is performed on the arrays acquired in steps S1 and S2 to improve the SN ratio (step S3). At this time, a correlation between the spreading code held in advance in the second wireless device 21 and the held sampling result is taken and despreading processing is performed, and the bit string of the obtained result is further stored in the storage unit Hold on.
Further, since the same data is repeatedly transmitted from the data transmitter 3, a majority decision process is performed between them, and the result is stored in the storage unit (step S4).

  Next, it is determined whether or not there is a clear error such as a parity bit being inverted in the result obtained after the majority process (step S5). If it is determined in step S5 that there is no clear error, the obtained result is output as data (second data) transmitted from the data transmitter 3 (step S6). On the other hand, if it is determined in step S5 that there is a clear error, it can be said that the data from the data transmitter 3 is in a transmission environment that is easily buried in noise.

  In such a case, the bit error rate at the soft decision / Viterbi output having a greater influence of disturbance is sampled (step S7). Then, the same processing as the processing from step S2 to step S4 is performed on the sampling result of the bit error rate at the soft decision / Viterbi output (step S8). Further, it is determined whether or not there is a clear error in the result after the majority processing, such as the parity bit being inverted (step S9). If it is determined in step S9 that there is no clear error, the obtained result is output as data (second data) transmitted from the data transmitter 3 (step S6).

  On the other hand, if it is determined in step S9 that there is a clear error, the bit error rate at the demapping output that is more affected by disturbance is sampled (step S10). Then, the same processing as the processing from step S2 to step S4 is performed on the sampling result of the bit error rate at the demapping output (step S11). Then, the obtained result is output as data (second data) transmitted from the data transmitter 3 (step S6).

The sampling becomes more sensitive to noise as the bit error rate at the frame processing output, the bit error rate at the soft decision / Viterbi output, and the bit error rate at the demapping output. In this case, the influence of noise can be reduced by increasing the length of the above spreading code or increasing the number of samplings in the majority process.
In addition, when it is limited to use in an environment with little noise, for example, an environment where the distance between the data transmitter 3 and the second wireless device 2 is short, there is no need to adopt the complicated configuration as described above, and frame processing By tracing only the subsequent error rate, the second data transmitted from the data transmitter 3 can be demodulated.

  Also in the wireless communication system according to the present embodiment, it is possible to provide a wireless communication system capable of reducing the cost when introducing a system using RFID technology in a wireless network environment.

  Note that the second wireless device 21 in the wireless communication system according to the present embodiment can also be configured by performing software processing on an existing wireless device. That is, since the process after the demapping process in the second wireless device 21 shown in FIG. 6 is a protocol process, for example, by performing a software process on the protocol processing unit shown in FIG. 4, the second process shown in FIG. Wireless device 21 can be configured. In the present embodiment, a part of the protocol processing unit shown in FIG. 4 may be configured by hardware. In this case, the software processing is applied to the second part other than the part configured by the hardware of the protocol processing unit. Wireless device 21 can be configured.

Embodiment 3
Next, a third embodiment of the present invention will be described. In the wireless communication system according to the present embodiment, the process in the second wireless device 21 shown in FIG. 6 is different from the process in the second embodiment. Since other than this is the same as in the case of the second embodiment, the same components are denoted by the same reference numerals, and redundant description is omitted.

  FIG. 10 is a flowchart for explaining processing of the second wireless device 21 according to the present embodiment. The difference between the flow shown in FIG. 7 described in the second embodiment and the flow shown in FIG. 10 is that the determination using the parity bits described in FIG. 7 (steps S5 and S9) is unnecessary in the flow shown in FIG. It is a point.

  That is, in the flow shown in FIG. 10, first, the bit error rate at the frame processing output is sampled (step S21). Then, the obtained sampling results are held in the storage unit in an array (step S22).

  Next, the code despreading process is performed on the arrays acquired in steps S21 and S22 to improve the SN ratio (step S23). At this time, a correlation between the spreading code held in advance in the second wireless device 21 and the held sampling result is taken and despreading processing is performed, and the bit string of the obtained result is further stored in the storage unit Hold on. Then, majority processing is performed using the data transmitted repeatedly from the data transmitter 3, and the result (result 1) is held in the storage unit (step S24).

Further, the following processing is performed in parallel with the processing of steps S21 to S24.
First, the bit error rate at the demapping output is sampled (step S25). Then, the obtained sampling results are held in the storage unit in an array (step S26).

  Next, the code despreading process is performed on the arrays acquired in steps S25 and S26 to improve the SN ratio (step S27). At this time, a correlation between the spreading code held in advance in the second wireless device 21 and the held sampling result is taken and despreading processing is performed, and the bit string of the obtained result is further stored in the storage unit Hold on. Then, majority processing is performed using the data transmitted repeatedly from the data transmitter 3, and the result (result 2) is held in the storage unit (step S28).

  Finally, the difference between the majority processing result 1 and the majority processing result 2 is output as data (second data) transmitted from the data transmitter (step S29).

  In this way, by taking the difference between the frame processing output that is less affected by the disturbance than the demapping output and the demapping output, the data transmitted as disturbance from the data transmitter 3 can be extracted. Moreover, in the radio | wireless communications system concerning this Embodiment, the process of the 2nd radio | wireless apparatus 21 can be simplified compared with the process concerning Embodiment 2. FIG.

Embodiment 4
Next, a fourth embodiment of the present invention will be described. The wireless communication system according to the present embodiment is different from the wireless communication system described in Embodiments 1 to 3 in that a plurality of data transmitters 3_1 to 3_N are provided. Except this, since it is the same as in the first to third embodiments, the same components are denoted by the same reference numerals, and redundant description is omitted.

  FIG. 11A is a block diagram showing a radio communication system according to the present embodiment. As shown in FIG. 11A, in the wireless communication system according to the present embodiment, a plurality of data transmitters 3_1 are within a range in which the first radio wave output from the first wireless device 1 can be received. ~ 3_N. The data transmitter 3_1 receives the first radio wave 13_1 output from the first wireless device 1, modulates the first radio wave 13_1 according to the second data to be transmitted, and the second radio wave 14_1. Is output. Similarly, the data transmitter 3_2 receives the first radio wave 13_2 output from the first wireless device 1, modulates the first radio wave 13_2 in accordance with the second data to be transmitted, The radio wave 14_2 is output. Similarly, the data transmitter 3_N receives the first radio wave 13_N output from the first wireless device 1, modulates the first radio wave 13_N according to the second data to be transmitted, The radio wave 14_N is output.

  FIG. 11B is a diagram illustrating an example of disturbance that each of the plurality of data transmitters 3_1 to 3_N gives to the first radio waves 13_1 to 13_N. As shown in FIG. 11B, each of the plurality of data transmitters 3_1 to 3_N adds identification information such as a spread code to the data to be transmitted as a header.

  The second wireless device 2 receives the first radio wave 12 and the second radio waves 14_1 to 14_N, and the first data transmitted from the first radio device 1 included in the received radio wave Each data transmitted from each of the data transmitters 3_1 to 3_N is separated and demodulated using the separation / demodulation circuit 24. Here, the separation / demodulation circuit 24 can distinguish each data transmitted from each data transmitter 3_1 to 3_N based on the identification information added as a header to the data to be transmitted. The data separated and demodulated by the separation / demodulation circuit 24 is output as demodulated data 25 from the first wireless device 1 and demodulated data 26_1 to 26_N from the data transmitters 3_1 to 3_N.

  In the above example, a spread code is used as the identification information. However, the identification information may be any information as long as it is information that can distinguish each data. For example, an M sequence can be used as the spreading code. However, the pseudo-random number having high autocorrelation is not particularly limited to the M sequence, and for example, a GOLD code can be used. In the second and third embodiments, the example in which the despreading process is performed has been described. In this case, the diffusion process for data identification is required prior to the despreading process.

For example, in the case of using a pseudo random number pattern that is a code sequence having a small autocorrelation as a spreading code, if it is PN4, there is one set of pseudo random number systems depending on the initial values allowed for the M sequence. On the other hand, if PN5 and PN7 are used, the number increases to 3 sets and 9 sets, respectively. Also, as shown in FIG. 12, when the autocorrelation of PN4 and PN5 is taken, the difference between the peak value and the bottom value of the correlation strength is 16 and 32, respectively, which are 24 dB and 30 dB, respectively. As a result, it is possible to distinguish data having another spreading code with higher accuracy than the S / N ratio required for demodulation of on / off keying with a bit error rate> 10 ⁻² .

  If the desired data transmitter and the second wireless device 2 are synchronized by adopting PN5 as the header and applying a matched filter at the beginning of data reception, three sets in the second wireless device 2 Even if there is a wireless chip, only data from one desired data transmitter can be selectively received. When there are four or more sets of data transmitters, data from each data transmitter can be selectively received by using a spreading code of PN7 or higher.

  With such a wireless communication system, even when there are a plurality of data transmitters 3_1 to 3_N, it is possible to avoid reception of interference and distinguish and receive each data transmitted from each data transmitter.

Embodiment 5
Next, a fifth embodiment of the present invention will be described. FIG. 13 is a diagram for explaining a problem that occurs when the communication distance is increased in the wireless communication system according to the first embodiment. As shown in FIG. 13, the waveform when the first radio wave 12 reaches the second wireless device is assumed to be expressed by a simple sine wave Asin (2πft). Here, A is the amplitude, f is the frequency of the signal output from the first radio equipment 1 (the light speed is c, the wavelength is c / f), and t is the time.

  In addition, the distance between the first wireless device 1 and the second wireless device 2 is R, the distance between the first wireless device 1 and the data transmitter 3 is r, the data transmitter 3 and the second wireless device 2 are If the distance is D, the path of the radio wave passing through the data transmitter 3 extends by r + D−R as compared to the path of the first radio wave 12. Therefore, the waveform when the first radio wave 13 is reflected by the data transmitter 3 and the reflected second radio wave 14 is input to the second wireless device 2 is attenuated by α (<1). Since the phase is delayed by Δφ, it is expressed as Aαsin (2πft + Δφ).

Therefore, the signal received by the second wireless device 2 is a signal obtained by adding the first radio wave 12 and the second radio wave 14 and can be expressed by the following equation.
Here, Ψ is a constant generated by addition, and is not used in the following discussion.

From Equation 1, if the factor (1 + 2αcos (Δφ) + α ² ) ^1/2 is greater than 1, the close phases overlap each other. In this state, when the first radio wave 12 and the second radio wave 14 are received by the second wireless device 2, the first radio wave 12 and the second radio wave 14 strengthen each other, so that the reception SN ratio is increased. Increase. For this reason, the bit error rate of the first data transmitted by the first wireless device 1 is lowered.

If the factor (1 + 2αcos (Δφ) + α ² ) ^1/2 is smaller than 1, the distant phases interfere with each other. In this state, when the first radio wave 12 and the second radio wave 14 are received by the second wireless device 2, the first radio wave 12 and the second radio wave 14 weaken each other. The bit error rate of the first data transmitted by the wireless device 1 is increased.

On the other hand, if the factor (1 + 2αcos (Δφ) + α ² ) ^1/2 is equal to 1, the amplitude does not change. Therefore, although the first radio wave 13 is reflected by the data transmitter 3, only the phase is changed and the amplitude and the bit error rate are not changed. That is, if factors (1 + 2αcos (Δφ) + α 2) 1/2 = 1 and becomes satisfies the following formula 2, because there is no change in the bit error rate, the data transmitter 3 described in the first embodiment using Cannot send data.

  As will be described in detail below, when the distance r increases, the above equation 2 may be satisfied depending on the condition of Δφ.

Since α included in the above formulas 1 and 2 is the voltage amplitude ratio between the first radio wave 12 and the second radio wave 14, the power strengths Pr and Pr of the first radio wave 12 and the second radio wave 14, respectively. It can be expressed by the following formula 3 using '.

If the power before the antenna emitted by the first wireless device 1 is Pt, and the antenna gains of the first wireless device 1 and the second wireless device 2 are Gt and Gr, respectively, the power intensity Pr of the first radio wave 12 is Frisse. From the propagation formula of

Further, if the reflection gain when the data transmitter 3 reflects the first radio wave 13 and outputs the second radio wave 14 is G, the power intensity Pr ′ of the second radio wave 14 is the same as the above equation 4. It is expressed as Equation 5. Note that G includes not only a circuit loss at the time of reflection but also an antenna gain in the data transmitter 3.

From the above formula 3, formula 4, and formula 5, the following formula 6 can be obtained.
That is, it can be seen from Equation 6 that the value of α is determined by the distances R, r, D, the reflection gain G, and the frequency f regardless of the antenna gains of the first wireless device 1 and the second wireless device 2.

Further, the phase difference Δφ at the frequency f included in the above formulas 1 and 2 is such that the path of the radio wave passing through the data transmitter 3 extends by r + D−R as compared to the path passing through the first radio wave 12. Can be expressed as:

Therefore, since D ² = R ² + r ² −2Rr cos θ from Equation 2, Equation 6, Equation 7, and the cosine theorem, the distance between the first wireless device 1 and the second wireless device 2 is R = 1 [m. ], The portion satisfying Expression 2 is as indicated by reference numeral 101 shown in FIG.

  As shown in FIG. 14, in the region close to the first wireless device 1 and the second wireless device 2, the condition of Expression 2 is not satisfied, so that a problem caused by no amplitude fluctuation, that is, the bit error rate does not change. The problem that data cannot be transmitted using the data transmitter 3 does not occur. On the other hand, when the data transmitter 3 is arranged in a region that is far from the first wireless device 1 and the second wireless device 2, the condition of Equation 2 may be satisfied, and therefore amplitude fluctuation occurs. The problem is due to the absence. In this case, a solution means described below is required.

  FIG. 15 is a block diagram showing a radio communication system according to the present embodiment. As shown in FIG. 15, in the radio communication system according to the present embodiment, the configuration of the modulation circuit 132 provided in the data transmitter 103 is different from that of the radio communication system described in the first embodiment. Other than this, it is the same as in the case of the first embodiment, so the same components are denoted by the same reference numerals, and redundant description is omitted.

  As shown in FIG. 15, the data transmitter 103 included in the wireless communication system according to the present embodiment includes an antenna 31, a modulation circuit 132, and a sensor 33. The data transmitter 103 receives the first radio wave 13 output from the first wireless device 1 by the antenna 31 and uses the modulation circuit 132 to respond to the second data to be transmitted according to the first radio wave 13. Are modulated to generate and output second radio waves 114_1 and 114_2.

  In other words, in the present embodiment, the modulation circuit 132 included in the data transmitter 103 includes the second radio wave 114_1 obtained by modulating the first radio wave 13 according to the second data to be transmitted, and the first radio wave to be transmitted. The first radio wave 13 is modulated in accordance with the data 2 and the second radio wave 114_2 whose phase is changed is generated and output. Here, the phase change is typically a phase delay. At this time, the distance that the second radio wave 114_1 and the second radio wave 114_2 propagate is equal to D. The second radio waves 114_1 and 114_2 are both received by the second wireless device 2.

  FIG. 16A is a block diagram illustrating details of the data transmitter 103 included in the wireless communication system according to the present embodiment. As shown in FIG. 16A, the modulation circuit 132 included in the data transmitter 103 includes load modulation circuits 134 and 135 and a phase change circuit 136.

  The modulation circuit 132 receives the first radio wave 13 output from the first wireless device 1 by the antenna 31, and the first radio wave 13 by the load modulation circuit 134 according to the second data generated by the sensor 33. Is modulated to generate and output the second radio wave 114_1. The modulation circuit 132 receives the first radio wave 13 output from the first wireless device 1 by the antenna 31, and the load modulation circuit 135 receives the first radio wave 13 from the first radio device 1 in accordance with the second data generated by the sensor 33. The radio wave 13 is load-modulated to generate and output a second radio wave 114_2. At this time, since the phase change circuit 136 is provided between the antenna 31 and the load modulation circuit 135, the output second radio wave 114_2 is delayed.

  FIG. 16B is a diagram illustrating an example of a specific circuit of the data transmitter 103 illustrated in FIG. As shown in FIG. 16B, the load modulation circuit 134 included in the modulation circuit 132 includes a capacitive element C1, a capacitive element C2, and a transistor Tr1 (eg, N-type). One end of the capacitive element C1 is connected to the antenna 31, and the other end is connected to the ground potential. One end of the capacitive element C2 is connected to the antenna 31, and the other end is connected to the drain of the transistor Tr1. The drain of the transistor Tr1 is connected to the other end of the capacitive element C2, the gate is connected to the output of the sensor 33, and the source is connected to the ground potential.

  The load modulation circuit 135 includes a capacitive element C3, a capacitive element C4, and a transistor Tr2 (eg, N-type). One end of the capacitive element C3 is connected to the phase change circuit 136, and the other end is connected to the ground potential. One end of the capacitive element C4 is connected to the phase change circuit 136, and the other end is connected to the drain of the transistor Tr2. The drain of the transistor Tr2 is connected to the other end of the capacitive element C4, the gate is connected to the output of the sensor 33, and the source is connected to the ground potential.

  The phase change circuit 136 includes a resistance element R1 and a capacitance element C5. One end of the resistance element R1 is connected to the antenna 31, and the other end is connected to the load modulation circuit 135. One end of the capacitive element C3 is connected to the load modulation circuit 135, and the other end is connected to the ground potential.

  The operation of the circuit shown in FIG. 16B is the same as the operation of the data transmitter 103 shown in FIG. Further, the data transmitter 103 may include the power generation circuit 34 as in the wireless communication system according to the first embodiment illustrated in FIG.

The data transmitter 103 having the above configuration can output the second radio wave 114_1 and the second radio wave 114_2 having different phases. At this time, a phase delay Δt is added to the second radio wave 114_2 by the phase change circuit 136. Therefore, a signal from the first radio wave 12 that directly reaches the second wireless device 2 from the first wireless device 1 and the second wireless device 2 from the first wireless device 1 via the data transmitter 103. The phase delay with respect to the signal due to the second radio wave 114_2 (with delay) that arrives can be expressed by the following Expression 8.

Similarly to the above, since D ² = R ² + r ² −2Rr cos θ from Expression 2, Expression 6, Expression 8, and the cosine theorem, the distance between the first wireless device 1 and the second wireless device 2 is R = When fixed at 1 [m], a portion satisfying Expression 2 is as indicated by reference numeral 102 (indicated by a broken line) shown in FIG.

  That is, the portion denoted by reference numeral 101 (shown by a solid line) in FIG. 17 corresponds to the portion denoted by reference numeral 101 in FIG. 14, and the condition of Expression 2 generated by the second radio wave 114_1 that is not delayed is satisfied. Corresponds to the part to be filled. On the other hand, a portion denoted by reference numeral 102 (shown by a broken line) in FIG. 17 corresponds to a portion that satisfies the condition of Expression 2 generated by the second radio wave 114_2 to which the phase delay Δt is added by the modulation circuit 132.

  At this time, in the portion denoted by reference numeral 101 (indicated by a solid line), since the second radio wave 114_1 transmitted from the data transmitter 103 satisfies the condition of Equation 2, data can be transmitted using the second radio wave 114_1. Can not. However, in the portion denoted by reference numeral 101 (shown by a solid line), the second radio wave 114_2 to which the phase delay Δt is added does not satisfy the condition of Equation 2, and therefore data can be transmitted using the second radio wave 114_2. .

  Similarly, in the portion denoted by reference numeral 102 (indicated by a broken line), since the second radio wave 114_2 transmitted from the data transmitter 103 satisfies the condition of Equation 2, data can be transmitted using the second radio wave 114_2. Can not. However, in the portion denoted by reference numeral 102 (indicated by a broken line), since the second radio wave 114_1 does not satisfy the condition of Expression 2, data can be transmitted using the second radio wave 114_1.

  Note that when the phase delay Δt coincides with the signal period 1 / f, the phases of the second radio wave 114_1 and the second radio wave 114_2 overlap. In this case, the problem that data cannot be transmitted using a data transmitter cannot be solved. Therefore, the phase delay Δt and the signal period 1 / f should not be matched. Even if the phases of the second radio wave 114_1 and the second radio wave 114_2 do not overlap, the amount of noise increases in communication performed by the data transmitter if these phases are close. Therefore, it is necessary to set the phase delay so that the phase of the second radio wave 114_1 and the second radio wave 114_2 are not close. Conversely, the phase overlap between the second radio wave 114_1 and the second radio wave 114_2 is the smallest when the phase delay Δt is half the signal period 1 / f. Considering this point, it is preferable to configure the phase change circuit 136 so that the phase delay Δt is half of the signal period 1 / f. The phase delay Δt in the phase change circuit 136 can be changed as appropriate by changing the resistance value of the resistance element R1 and the capacitance value of the capacitance element C5.

  In the present embodiment, the case where the data transmitter 103 outputs two second radio waves 114_1 and 114_2 having different phases has been described. However, there may be two or more second radio waves output from the data transmitter 103 and having different phases. That is, by outputting at least two radio waves with different phases from the data transmitter 103, the above problem that data cannot be transmitted using the data transmitter can be solved.

  As described above, the invention according to the present embodiment can provide a wireless communication system that can always transmit data regardless of the position of the data transmitter.

Embodiment 6
Next, a sixth embodiment of the present invention will be described. Similarly to the fifth embodiment, the invention according to the present embodiment is an invention for solving the problem that data cannot be transmitted from the data transmitter when the condition of Expression 2 is satisfied. In the wireless communication system according to the present embodiment, the configuration of the data transmitter is different from the configuration of the data transmitter 103 shown in FIG. 15 described in the fifth embodiment. Since other than this is the same as in the fifth embodiment and FIG.

  FIG. 18A is a block diagram showing the data transmitter 203 included in the wireless communication system according to the present embodiment. As shown in FIG. 18A, the data transmitter 203 includes antennas 31_1 and 31_2, a modulation circuit 232, and a sensor 33. The sensor 33 has the same configuration as that of the first embodiment. The modulation circuit 232 includes a load modulation circuit 234 and a phase change circuit 236.

  The modulation circuit 232 receives the first radio wave 13 output from the first wireless device 1 by the antenna 31_1, and the load modulation circuit 234 receives the first radio wave 13 according to the second data generated by the sensor 33. Is modulated to generate a second radio wave 114_1 and output from the antenna 31_1. Also, the modulation circuit 232 receives the first radio wave 13 output from the first wireless device 1 by the antenna 31_2, and the load modulation circuit 234 generates the first radio wave 13 according to the second data generated by the sensor 33. The radio wave 13 is load-modulated to generate a second radio wave 114_2 and output from the antenna 31_2. At this time, since the phase change circuit 236 is provided between the antenna 31_2 and the load modulation circuit 234, the output second radio wave 114_2 is delayed.

  In addition, since the distance between the antenna 31_1 and the antenna 31_2 is sufficiently short, the distance between the antenna 31_1 and the first wireless device 1 and the distance between the antenna 31_2 and the first wireless device 1 are both r. Similarly, the distance between the antenna 31_1 and the second wireless device 2 and the distance between the antenna 31_2 and the second wireless device 2 are both D.

  Also in the present embodiment, as in the fifth embodiment, since at least two second radio waves 114_1 and 114_2 having different phases can be output from the data transmitter 203, when the condition of Expression 2 is satisfied, The problem that data cannot be transmitted using a data transmitter can be solved.

  FIG. 18B is a diagram illustrating an example of a specific circuit of the data transmitter 203 illustrated in FIG. As shown in FIG. 18B, the load modulation circuit 234 included in the modulation circuit 232 includes a capacitive element C6, a capacitive element C7, and a transistor Tr3 (for example, N-type). One end of the capacitive element C6 is connected to the antenna 31_1, and the other end is connected to the ground potential. One end of the capacitor C7 is connected to the antenna 31_1, and the other end is connected to the drain of the transistor Tr3. The drain of the transistor Tr3 is connected to the other end of the capacitive element C7, the gate is connected to the output of the sensor 33, and the source is connected to the ground potential.

  The phase change circuit 236 includes a resistance element R2 and a capacitance element C8. One end of the resistance element R2 is connected to the antenna 31_2, and the other end is connected to the load modulation circuit 234. One end of the capacitive element C8 is connected to the load modulation circuit 234, and the other end is connected to the ground potential.

  The operation of the circuit shown in FIG. 18B is the same as the operation of the data transmitter 203 shown in FIG. The data transmitter 203 may include the power generation circuit 34 as in the wireless communication system according to the first embodiment illustrated in FIG.

  In this embodiment, it is only necessary that a phase delay of Δt occurs between the component reflected by the antenna 31_1 (second radio wave 114_1) and the component reflected by the antenna 31_2 (second radio wave 114_2). Therefore, instead of providing the phase change circuit 236, a delay may be added to the component reflected by the antenna 31_2 using the parasitic inductance, parasitic resistance, and parasitic capacitance of the antenna 31_2.

  However, in this case, in order to prevent interference between the antenna 31_1 and the antenna 31_2 and hindering communication, the arrangement interval of the antennas is increased, or the null point of the antenna 31_1 is changed from the lobe of the antenna 31_2. It is preferable to arrange them orthogonally. Further, in this case, since different delays are added to the signals between the antenna 31_1 and the antenna 31_2, a difference occurs in the shape such as the number of turns and the area of the antenna. Therefore, it is different from the conventional diversity antenna having the same shape.

  As described above, the invention according to the present embodiment can provide a wireless communication system that can always transmit data regardless of the position of the data transmitter.

Embodiment 7
Next, a seventh embodiment of the present invention will be described. Similarly to the fifth embodiment, the invention according to the present embodiment is an invention for solving the problem that data cannot be transmitted from the data transmitter when the condition of Expression 2 is satisfied. In the wireless communication system according to the present embodiment, the configuration of the data transmitter is different from the configuration of the data transmitter 103 shown in FIG. 15 described in the fifth embodiment. Since other than this is the same as in the fifth embodiment and FIG.

  FIG. 19A is a block diagram showing a data transmitter 303 included in the wireless communication system according to the present embodiment. As shown in FIG. 19A, the data transmitter 303 includes an antenna 31, a modulation circuit 332, and a sensor 33. The sensor 33 has the same configuration as that of the first embodiment. The modulation circuit 332 includes a load modulation circuit 234, a switch 335, and a phase change circuit 236. FIG. 19B is a diagram illustrating an example of a specific circuit of the data transmitter 303 illustrated in FIG. Here, the configurations and operations of the load modulation circuit 234 and the phase change circuit 236 are the same as the configurations and operations of the load modulation circuit 234 and the phase change circuit 236 described in the sixth embodiment (FIGS. 18A and 18B). b)).

  The switch 335 illustrated in FIGS. 19A and 19B connects the antenna 31 and the load modulation circuit 234 during the first period. The switch 335 connects the antenna 31 and the phase change circuit 236 during the second period.

  During the first period, the modulation circuit 332 receives the first radio wave 13 output from the first wireless device 1 by the antenna 31, and the load modulation circuit according to the second data generated by the sensor 33. At 234, the first radio wave 13 is load-modulated to generate a second radio wave 114_1 and output from the antenna 31.

  In addition, during the second period, the modulation circuit 332 receives the first radio wave 13 output from the first wireless device 1 by the antenna 31, and loads according to the second data generated by the sensor 33. The first radio wave 13 is load-modulated by the modulation circuit 234 to generate the second radio wave 114_2 and output from the antenna 31. At this time, since the phase change circuit 236 is provided between the antenna 31 and the load modulation circuit 234, the output second radio wave 114_2 is delayed.

  In this embodiment, the operation in the first period and the operation in the second period are alternately repeated, so that the second radio wave 114_1 and the delayed second radio wave 114_2 are transmitted from the antenna 31. Can be output in splits. That is, T = t1 + t2, where T is a predetermined transfer period of the first data by the first radio wave 13, t1 is the first period, and t2 is the second period. At this time, the data transmitter 303 outputs the second radio wave 114_1 during the first period t1, and outputs the delayed second radio wave 114_2 during the second period t2. In this case, the time division speed needs to exceed the data communication speed of data transmitted from the data transmitter 303.

  As described above, in this embodiment, the second radio wave 114_1 and the delayed second radio wave 114_2 are output from the data transmitter 303 in a time division manner. For this reason, in the region that satisfies the condition of Equation 2 (portions indicated by reference numerals 101 and 102 in FIG. 17), the data transfer rate from the data transmitter is t2 / T as compared with the case of the sixth embodiment. Become.

  On the other hand, in this embodiment, since the second radio wave 114_1 and the delayed second radio wave 114_2 can be output in a time-sharing manner as described above, the antenna is compared with the case of the sixth embodiment. The number can be reduced. Therefore, the area of the antenna occupying the data transmitter can be reduced. For example, this effect becomes significant when the frequency of the radio communication system is low and the antenna is large.

Embodiment 8
Next, an eighth embodiment of the present invention will be described. Similarly to the fifth embodiment, the invention according to the present embodiment is an invention for solving the problem that data cannot be transmitted from the data transmitter when the condition of Expression 2 is satisfied. In the wireless communication system according to the present embodiment, the configuration of the data transmitter is different from the configuration of the data transmitter 103 shown in FIG. 15 described in the fifth embodiment. Since other than this is the same as in the fifth embodiment and FIG.

  FIG. 20A is a block diagram showing a data transmitter 403 included in the wireless communication system according to the present embodiment. As shown in FIG. 20A, the data transmitter 403 includes an antenna 31, a modulation circuit 432, and a sensor 33. The modulation circuit 432 includes a delay circuit 436, a selector 437, a timing generation circuit 438, and a load modulation circuit 439.

  The selector 437 is supplied with the second data generated by the sensor 33 and the second data (with delay) obtained by adding a delay to the second data generated by the sensor 33 by the delay circuit 436. The The timing signal generated by the timing generation circuit 438 is supplied to the selector 437. The selector 437 delays the second data generated by the sensor 33 and the second data generated by the sensor 33 by the delay circuit 436 in accordance with the timing signal generated by the timing generation circuit 438. One of the added second data is output to the load modulation circuit 439.

  For example, the selector 437 outputs the second data generated by the sensor 33 to the load modulation circuit 439 during the first period. In addition, the selector 437 outputs, to the load modulation circuit 439, second data obtained by adding a delay by the delay circuit 436 to the second data generated by the sensor 33 during the second period.

  During the first period, the load modulation circuit 439 performs load modulation on the first radio wave 13 received by the antenna 31 according to the second data output from the selector 437 to generate a second radio wave 114_1 to generate the antenna. 31 to output. Further, the load modulation circuit 439 performs load modulation on the first radio wave 13 received by the antenna 31 during the second period according to the second data (with delay) output from the selector 437, and performs the second modulation. A radio wave 114_2 is generated and output from the antenna 31.

  FIG. 20B is a diagram illustrating an example of a specific circuit of the data transmitter 403 illustrated in FIG. As shown in FIG. 20B, the delay circuit 436 can be configured using two inverters. The timing generation circuit 438 can be configured using a ring oscillator in which a plurality of inverters are connected in a ring shape. The selector 437 can be configured using NANDs 1 to 3 and an inverter INV1. The load modulation circuit 439 can be configured using the capacitor C9, the capacitor C10, and the transistor Tr4.

  In this embodiment, the operation in the first period and the operation in the second period are alternately repeated, so that the second radio wave 114_1 and the delayed second radio wave 114_2 are transmitted from the antenna 31. Can be output in splits. That is, T = t1 + t2, where T is a predetermined transfer period of the first data by the first radio wave 13, t1 is the first period, and t2 is the second period. At this time, the data transmitter 403 outputs the second radio wave 114_1 during the first period t1, and outputs the delayed second radio wave 114_2 during the second period t2. In this case, the timing generated by the timing generation circuit 438, that is, the time division speed, needs to exceed the data communication speed of the data transmitted from the data transmitter 403.

  As described above, in the present embodiment, the second radio wave 114_1 and the delayed second radio wave 114_2 are output from the data transmitter 403 in a time division manner. For this reason, in the region that satisfies the condition of Equation 2 (portions indicated by reference numerals 101 and 102 in FIG. 17), the data transfer rate from the data transmitter is t2 / T as compared with the case of the sixth embodiment. Become.

  On the other hand, in this embodiment, since the second radio wave 114_1 and the delayed second radio wave 114_2 can be output in a time-sharing manner as described above, the antenna is compared with the case of the sixth embodiment. The number can be reduced. Therefore, the area of the antenna occupying the data transmitter can be reduced. For example, this effect becomes significant when the frequency of the radio communication system is low and the antenna is large.

Other Embodiments Hereinafter, other embodiments will be described.
The data transmitter described in the above embodiment may be manufactured on a semiconductor chip. That is, each circuit (modulation circuit, sensor, etc.) constituting the data transmitter may be manufactured on a semiconductor chip. In this case, the antenna may be formed on the same chip as the semiconductor chip on which each circuit included in the data transmitter is formed. Further, an antenna may be formed separately from the semiconductor chip on which each circuit included in the data transmitter is formed.

  As shown in FIG. 21A, a data transmitter 501 manufactured using a semiconductor chip can be attached to an object to be measured using an adhesive member 504. As the adhesive member 504, for example, a bandage can be used. Here, the data transmitter 501 includes circuits 502 and an antenna 503 constituting the data transmitter. For example, when the data transmitter 501 includes a temperature sensor, the chip-shaped data transmitter 501 is attached to the adhesive member 504, and the adhesive member 504 is attached to the measurement target, thereby easily measuring the temperature of the measurement target. can do.

  The adhesive member cannot be used after a predetermined time has passed since its adhesive strength decreases with time. On the other hand, the product life of the data transmitter 501 is long. Therefore, the data transmitter 501 can be reused by configuring the adhesive member 504 so that the data transmitter 501 can be removed. For example, the data transmitter 501 can be removed by forming a pocket in the adhesive member 504.

  FIG. 21B is a cross-sectional view of the adhesive member. As shown in FIG. 21B, when the data transmitter 501 includes a temperature sensor, the thermal conductivity of the member 505 positioned between the data transmitter 501 attached to the adhesive member 504 and the measurement target. It is preferable to use a material having a high value. Thus, the temperature of the object to be measured can be accurately measured by using a material having high thermal conductivity. Here, as a material having high thermal conductivity, a metal material such as copper, a resin material having high thermal conductivity, or the like can be used.

  The data transmitter may be provided in the thermometer. In this case, you may use the temperature sensor with which a thermometer is provided as a sensor of a data transmitter. By providing the data transmitter in the thermometer, the history of the temperature of the measurement target can be transmitted to the second wireless device 2.

  Next, features of the data transmitter described in the above embodiment will be described.

  A data transmitter according to the present invention modulates a first radio wave used in a wireless network in accordance with a sensor for acquiring data to be transmitted and the data to be transmitted. And a modulation circuit that generates a second radio wave that gives disturbance to the radio wave.

  The data transmitter according to the present invention outputs at least two second radio waves having different phases.

  The modulation circuit modulates the phase by changing the second radio wave modulated by the first radio wave according to the second data to be transmitted and the first radio wave 13 according to the second data to be transmitted. The generated second radio wave is generated and output.

  As shown in FIG. 16A, the modulation circuit 132 includes a load modulation circuit 134 that performs load modulation on the first radio wave 13 received by the antenna 31 according to the second data generated by the sensor 33, and a sensor. A load modulation circuit 135 that performs load modulation on the first radio wave 13 received by the antenna 31 according to the second data generated by the antenna 33, and a phase change circuit 136 provided between the antenna 31 and the load modulation circuit 135. And comprising. Then, the second radio wave 114_2 that is load-modulated by the load modulation circuit 135 that is output from the antenna 31 is delayed.

  As shown in FIG. 18 (a), the data transmitter according to the present invention includes antennas 31_1 and 31_2 that receive the first radio wave 13 and antennas 31_1 according to the second data generated by the sensor 33, respectively. , 31_2, a load modulation circuit 234 that performs load modulation on the first radio wave 13 and a phase change circuit 236 provided between the antenna 31_2 and the load modulation circuit 234. Then, the second radio wave 114_2 that is load-modulated by the load modulation circuit 235 output from the antenna 31_2 is delayed.

  As shown in FIG. 19A, the modulation circuit 332 includes a load modulation circuit 234 that performs load modulation on the first radio wave 13 received by the antenna 31 in accordance with the second data generated by the sensor 33, and A switch 335 is provided that connects the antenna 31 and the load modulation circuit 234 during the first period and connects the antenna 31 and the load modulation circuit 234 via the phase change circuit 236 during the second period. During the first period, load-modulated second radio wave 114_1 is output from antenna 31. During the second period, load-modulated and delayed second radio wave 114_2 is output from antenna 31.

  As shown in FIG. 20A, the modulation circuit 432 includes a second data generated by the sensor 33 and a second data obtained by adding a delay to the second data generated by the sensor 33 by the delay circuit 436. And a selector 437 that outputs one of the second data and the second data to which the delay is added according to the timing signal generated by the timing generation circuit 438, And a load modulation circuit 434 that performs load modulation on the first radio wave 13 received by the antenna 31 in accordance with the output of the selector 437. During the period in which the selector 437 outputs the second data with the delay added, the second radio wave 114_2 that is load-modulated and delayed is output from the antenna 31.

  The data transmitter is formed on a semiconductor chip.

  Next, features of the second wireless device described in the above embodiment will be described.

  The second wireless device according to the present invention is generated by modulating the first radio wave in accordance with the first radio wave including the first data and the second data, and disturbs the first radio wave. And receiving and demodulating the first data and the second data contained in the received radio wave based on the bit error rate of the first radio wave Separating and demodulating circuit.

  The separation demodulation circuit included in the second wireless device according to the present invention includes: a demodulation circuit that demodulates the first data; and an evaluation of a bit error rate after demodulating the first data, and the bit error rate And an error rate evaluation circuit that demodulates the second data based on the time variation of

  The separation / demodulation circuit included in the second wireless device according to the present invention is configured by performing software processing on a protocol processing unit included in the wireless device.

  Although the present invention has been described with reference to the above embodiment, the present invention is not limited to the configuration of the above embodiment, and can be made by those skilled in the art within the scope of the invention of the claims of the claims of the present application. It goes without saying that various modifications, corrections, and combinations are included.

1 First wireless device 2, 20, 21, 22 Second wireless device 3, 103, 203, 303, 403 Data transmitter 11, 23, 31, 31_1, 31_2 Antenna 12 First radio wave (direct wave)
13 First radio wave 14 Second radio wave 24 Separation / demodulation circuit 25 Demodulated data from first wireless device 26 Demodulated data from data transmitter 27 Amplifier 28 Baseband filter 32 Modulation circuit 33 Sensor 34 Power generation circuit 41 Demodulation circuit 42 Error rate evaluation circuit 81 Reception circuit 82 Protocol processing unit 132, 232, 332, 432 Modulation circuit 134, 135, 234, 439 Load modulation circuit 136, 236 Phase change circuit 335 Switch 436 Delay circuit 437 Selector 438 Timing generation circuit

Claims (16)

A first wireless device that transmits first data using a first radio wave;
A data transmitter that outputs a second radio wave generated by modulating the first radio wave according to second data to be transmitted;
While receiving the first radio wave and the second radio wave, the first data transmitted from the first wireless device included in the received radio wave and the data transmitted from the data transmitter A second wireless device including a separation demodulation circuit for separating and demodulating the second data ,
The data transmitter changes the bit error rate of the first radio wave by giving a disturbance to the first radio wave according to the second data,
The second wireless device demodulates the second data transmitted from the data transmitter based on a change in the bit error rate of the first radio wave;
Wireless communication system.   The wireless communication system according to claim 1, wherein the data transmitter generates the second radio wave by load-modulating the first radio wave. The wireless communication system according to claim 1 or 2 , wherein the data transmitter changes a bit error rate of the first radio wave within a range lower than a wireless standard value of a bit error rate. The modulation period of the second bit error rate for transmitting data of the first slower than the modulation period of the first radio wave for transmitting data, as claimed in any one of claims 1 to 3 radio Communications system. The separation demodulation circuit included in the second wireless device includes a demodulation circuit that demodulates the first data transmitted from the first wireless device, and the first circuit transmitted from the first wireless device. perform an assessment of the bit error rate after demodulation data, according to claim 1 and an error rate evaluation circuit for demodulating the second data transmitted from the data transmitter on the basis of the time variation of the bit error rate The radio | wireless communications system as described in any one of thru | or 4 . The error rate evaluation circuit includes a bit error rate of a frame processing output after demodulating the first data transmitted from the first wireless device, a bit error rate at a soft decision / Viterbi output, and a demapping output The wireless communication system according to claim 5 , wherein the second data transmitted from the data transmitter is demodulated using at least one of the bit error rates. The error rate evaluation circuit transmits the data based on a difference between a bit error rate in a frame processing output and a bit error rate in a demapping output after demodulating the first data transmitted from the first wireless device. The wireless communication system according to claim 5 , wherein the second data transmitted from a device is demodulated. The error rate evaluation circuit performs majority processing and code spreading on at least one of the bit error rate of the frame processing output, the bit error rate at the soft decision / Viterbi output, and the bit error rate at the demapping output The wireless communication system according to claim 6 , wherein at least one of the processes is performed. 8. The error rate evaluation circuit performs at least one of majority processing and code spreading processing on at least one of the bit error rate of the frame processing output and the bit error rate of the demapping output. The wireless communication system described.   The wireless communication system includes a plurality of the data transmitters, and the second wireless device transmits the second data based on identification information provided to the second data by each of the data transmitters. The wireless communication system according to any one of claims 1 to 9, wherein an origin is identified.   The wireless communication system according to any one of claims 1 to 10, wherein the data transmitter includes a sensor for acquiring the second data to be transmitted.   The wireless communication system according to any one of claims 1 to 11, wherein the data transmitter includes a power generation circuit that generates power using the first radio wave.   The wireless communication system according to any one of claims 1 to 12, wherein the separation / demodulation circuit is configured by performing software processing on a protocol processing unit included in the second wireless device. A wireless communication method for transmitting second data using a data transmitter to a wireless network including a first wireless device that transmits first data and a second wireless device that receives the first data. And
Transmitting the first data from a first wireless device using a first radio wave;
In the data transmitter, the first radio wave is modulated according to the second data to generate a second radio wave, and the second radio wave is output.
The first data and the data transmitted from the first wireless device included in the received radio wave while the second radio device receives the first radio wave and the second radio wave. Separating and demodulating the second data transmitted from the transmitter ;
The data transmitter changes the bit error rate of the first radio wave by giving a disturbance to the first radio wave according to the second data,
The second wireless device demodulates the second data transmitted from the data transmitter based on a change in the bit error rate of the first radio wave;
Wireless communication method.   The wireless communication method according to claim 14, wherein the data transmitter generates the second radio wave by load-modulating the first radio wave.   Receiving a first radio wave including first data and a second radio wave generated by modulating the first radio wave according to second data and causing disturbance to the first radio wave And a separation / demodulation circuit that separates and demodulates the first data and the second data contained in the received radio wave based on the bit error rate of the first radio wave.